Using a variety of histological and histochemical procedures, at the light and EM levels, we propose to test the hypothses that some genetically-determined abnormalites of neural crest development result from changes in the temporal and spatial patterns of synthesis, deposition and removal of glycosaminoglycans and other constituents (e.g. collagen(s)) of the extra-cellular matrix materials affect the morphogenetic behavior and differentiation of neural crest cells in vivo.